The present exemplary embodiment relates to a cleaning system for a cylindrical roller and, more particularly, to a fuser apparatus for an electrophotographic printing device which includes a cleaning system for cleaning the fuser roll of toner particles. It will be appreciated, however, that the web cleaning system finds application in the cleaning or in liquid application treatment of other cylindrical rollers.
In typical electrophotographic image forming devices, such as copy machines and laser beam printers, a photoconductive insulating member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within the document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a marking material. Generally, the marking material comprises pigmented toner particles adhering triboelectrically to carrier granules, which is often referred to simply as toner. The developed image is subsequently transferred to the print medium, such as a sheet of paper. The fusing of the toner image onto paper is generally accomplished by applying heat and pressure. A typical fuser assembly includes a fuser roll and a pressure roll, which define a nip therebetween. The side of the paper having the toner image typically faces the fuser roll, which is often supplied with a heat source, such as a resistance heater, at its core. The combination of heat from the fuser roll and pressure between the fuser roll and the pressure roll fuses the toner image to the paper, and once the fused toner cools, the image is permanently fixed to the paper.
Fuser assemblies typically include a cleaning system by which the fuser roll can be automatically cleaned and/or supplied with a lubricant or release agent. In some cleaning devices, a cloth web is urged against the surface of the fuser roll by a spring loaded foam tension roll at a location generally away from the nip formed by the pressure and fuser rolls. The web provides a textured surface for removing particles of toner that remained on the fuser roll after the paper with the toner image has passed through the fuser. The web may also be impregnated to provide amounts of lubricant or release agent to the fuser roll. Release agents generally function to prevent sheets of paper from sticking to the surface of the fuser roll, thus causing a paper jam. The release agents may also serve to minimize the amount of toner that sticks to the fuser roll. After a predetermined number of reproductions have been printed, the web is advanced a few millimeters from a supply roll towards an uptake roll to provide a clean web surface in contact with the surface to be cleaned.
Where high volumes of similar images or high area coverage images are to be printed and fused, there is a tendency for toner to build up on the web and hamper subsequent cleaning of the fuser roll. The problem of short term web saturation is particularly apparent in printing of electronic documents, which have the same layout and spacing so that image lines (e.g., from email headers, text lines, and tables) form layouts and halftone dot patterns where the image is laid down on the sheet with a high accuracy in registration. The toner on a saturated web may be transferred back to the fuser roll and be deposited on a subsequent sheet. This can cause visible defects in the printed copies. Spots and strings of toner can also be deposited on the stripper fingers and temperature sensors of the fuser assembly. The toner can also be transferred to the pressure roll, particularly after a pause in printing when rotation of the pressure and fuser rolls is recommenced. The toner is transferred from the pressure roll to the back side of the first copy and leads a user to request a servicing of the printer.